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standard-camera-app

A demo Expo app and a local Expo module (standard-camera) that implement a small, deliberately spec-shaped subset of the W3C Media Capture and Streams specification on iOS. The hypothesis being tested is that if a browser API is small enough and well-shaped, you can port it 1:1 to React Native and let DOM-first code run unchanged:

const stream = await navigator.mediaDevices.getUserMedia({ video: true });
videoRef.srcObject = stream;

That is the exact code you would write in a browser, and it works on iOS in this app.

This is a learning exercise, not a production library. See llp/0000-standard-camera.explainer.md for the full motivation and architecture.

Scope

The module ships navigator.mediaDevices.getUserMedia(), MediaStream, MediaStreamTrack, and a <Video> component whose srcObject setter binds an AVCaptureSession to an AVCaptureVideoPreviewLayer. Both { video: true } and { audio: true } (and the combined form) work. The clause-by-clause inventory of what is in and out lives in llp/0002-spec-subset-scope.spec.md.

Out of scope for v1: Android, getDisplayMedia, MediaRecorder, depth tracks, and WebXR. The repo does contain research-only WebXR-shaped LiDAR demos (see LLPs 0013–0015), but those are not part of the polyfilled surface.

Repo layout

  • src/app/ — Expo Router screens for the demo app, including the camera preview, in-app WPT runner, and the WebGPU, LiDAR, panorama, and neural-lens demos.
  • modules/standard-camera/ — the local Expo module. TypeScript polyfill in src/, Swift implementation in ios/.
  • llp/ — Linked Literate Programming documents. Start at LLP 0000. Design decisions, spec slices, and demo plans live here.
  • scripts/ — test-ios.ts, test-web.ts, and the panorama validation runner.

Quick start

This repo uses Bun:

bun install
bun run ios       # build and run on an iOS simulator
bun run web       # start the Expo Web bundler

For physical-device builds and the install-retry workflow, see AGENTS.md. The app requires iOS 16.4 or newer and has NSCameraUsageDescription and NSMicrophoneUsageDescription set in app.json.

Testing

The in-app WPT-style runner is the source of truth for spec compliance. To run it end to end on a simulator:

bun run test:ios

This boots iOS 26, installs the app, deep-links to the test runner, parses results from the simulator log, and shuts the simulator down. A spec change is not "done" until the runner is green. See llp/0010-in-app-wpt-runner.guide.md.

For an Expo Web smoke test that exercises the app shell, bundler, and browser console without emulating the iOS backend:

bun run test:web

The default web smoke test does not request camera permission. See llp/0011-expo-web-testing-flow.guide.md.

Demos

The (demo) tab in the app collects a few things built on top of the polyfilled camera stream:

  • A plain <Video srcObject={stream} /> preview that mirrors the browser API.
  • WebGPU shader-lens demos that sample camera frames as textures (LLP 0012).
  • A LiDAR depth demo behind a research-only WebXR-shaped API (LLPs 0013–0014).
  • A panoramic scene-capture demo (LLP 0015).
  • TFJS- and MobileNet-based on-device scene classification.

Contributing

Read the LLP for the area you are touching before changing code, and update the LLP in the same change. Every load-bearing implementation detail that exists because a spec clause says so should carry an @ref LLP NNNN#anchor comment. Run the ref-check skill before requesting review.

Agent and contributor guidance lives in AGENTS.md.